Answering a question about inclement shuttle landings, OrganicMarble quotes from a summary of landing rules:

The peak crosswind cannot exceed 15 knots, 12 knots at night. If the mission duration is greater than 20 days, the limit is 12 knots, day and night.

What is it about long duration missions that reduces the risk tolerance for a daytime landing?


1 Answer 1


Mission planners were worried about the pilot and commander losing flying proficiency and/or being affected by extended free fall on long missions.

Flight rule rationale section:

Crosswind limits for EDO flights and night landings include a somewhat arbitrary reduction to 12 knots peak to allow for additional piloting margin due to uncertainties in pilot performance degradation from increased exposure to zero-g and reduced depth perception, respectively.

Space Shuttle Flight Rules page 2-22

(EDO stands for Extended Duration Orbiter and refers to a suite of Orbiter modifications and add-ons which allowed extra long missions)

Note that this rule was never invoked for mission duration; the longest shuttle mission was STS-80 at 17 days, 15 hours, 53 minutes, which included two days of weather wave-offs.

  • $\begingroup$ That certainly makes sense - do you know why the crosswind for night landings wasn't also reduced? (e.g. maybe at 12 knots the effects are already small enough that further reduction wouldn't appreciably increase safety?) $\endgroup$ Commented Nov 23, 2019 at 2:19
  • $\begingroup$ I think you are correct. They even admit the reduction is "somewhat arbitrary". The rationale paragraph in the flight rules is pretty long and goes into more detail. $\endgroup$ Commented Nov 23, 2019 at 2:20
  • $\begingroup$ They should have played flight simulator on orbit :-) Not entirely joking... for the non-physiological aspects, simulation might be a reasonable approach to currency refresh. Automatic landing might be another, if politicly touchy. Or auto landing if simulator proficiency doesn't compare to previous metrics on the ground? $\endgroup$ Commented Nov 24, 2019 at 21:24
  • $\begingroup$ @ChrisStratton they kinda did - see my answer here space.stackexchange.com/questions/25195/… $\endgroup$ Commented Nov 24, 2019 at 21:26

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